Method of making chrome steel having various carbon contents



Patented Mar. 17, 1925.

UNITED STATES v PATENT OFFICE.

NAPOLEON PETINOT, OF NEW YORK, N. Y., ASSIGNOR TO UNITED STATES FERROALLOYS CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD MAKING CHROME STEEL HAVING VARIOUS CARBON CONTENTS.

No Drawing.

ticularly it relates to the manufacture of chrome steel rades havingsuch carbon contents as may e desired, particularly as carried out bymeans of the basic open hearth processes. k

The general practice in making alloy steel, which is familiar. to thoseskilled in the art of making steel by means of the 2 open hearthprocess, is as follows:

A charge of pig iron and iron scrap is made in such proportion that whenthe bath is melted, the carbon content in it will be from about one percent to 1.50%. To this charge is added limestone, and iron ore. Then themetal of the charge is held in the furnace, and the carbon is graduallyoxidized on account of the oxidizin atmosphere existing there. Usuallythere is a slight silicon content in the bath, which comes from the pigiron or from the scrap, and this usually varies from .75% to 1.25%. Suchslight silicon content is oxidized first so that there is no siliconpresent in the molten bath, and the bath is an oxidized bath.

It is further recognized by the art that any addition of ferrochromemade in lump form will become oxidized. during the time it is meltingand being diffused through the molten bath therebycreating a loss inchromium of from 10% to 40%. The extent of this loss depends on thedegree of heat existing in the molten bath, or more generallyspeaking,it depends on the amount of iron oxide contained in it.

It is the principal object of my invention to provide a process, whichwill substantially prevent such loss of chromium, and at the same timeprovide an inexpensive and efiicient method of making the chrome steelof any desired grade and of any desired carbon content.

Other advantages than those above set forth will be apparent to thoseskilled in Application filed January 30, 1924. Serial No. 689,566.

the art of making steel by means of the open hearth process.

In carrying out my invention, I follow the initial step of the previouspractices of the art, and prepare a charge of pig iron and iron scrap insuch proportion that when the bath is melted, the proper amount ofcarbon desired will be present. I then make an addition to the bath offerrosilicon of the grade known in the trade as Bessemer ferrosilicon,having a silicon content varying from 10% to 20%. This .ferrosilicon iscast in sha e form in a permanent mold as described in United StatesLetters Pat ent No. 1,274,360, issued to me July 30, 1918. Suflicientferrosilicon must be added to the bath to deoxidize it, andin practice,I have found that from one pound to two pounds of silicon added asferrosilicon is necessary to accomplish this end. When sufiicientsilicon has thus been added that fact will be apparent since then thebath'will lay quiet instead of boiling; Since the atmosphere isoxidizing, if the bath is kept as such for a long time, the siliconaddition will not only deoxidize the bath but the bath of carbon steelwill eventually reoxidize. This deoxidation will tak place according tothe equation oxidizes the bath but inasmuch as it has been added inexcessive quantities, it will prevent 'any possible reoxidation. Thelump ferrochrome which floats in the bath will first become mushy; thenit will melt, but it will notoxidize for the reason that the silicon hasmore aifinity :t'or oxygen or oxide, and consequently will oxidizefirst, It. is for this reason that the excessive amount of ferrosiliconis necessary.

The addition of the ferrosilicon with the loo.

content of from 10% to 20% will protect the chromium fromoxidation thusgiving a better yield. This is the great advantage of my invention.Obviously, as soon as the chromium is melted other additions of ferroallo s such as ferromanganese may be made as esired either into thefurnace or to the ladle and then the heat is tapped.

In practicing my process, I add enough silicon not only to deoxidize thebath but also to protect from oxidation the addition of chromium. Thecondition that enough silicon has been added to thoroughly deoxidize thebath is easily recognized since when that has been done the. .bath thenlays quiet or is dead In practice I usually add ferrochrome from fiveminutes to fifteen minutes after the to ferro'silicon addition has ing asilicon content of from 10% to 20% to kill all boiling action in thefurnace and then add ferrochrome to the bath.

2. A process of the character described comprising the addition to abath composed of pig iron and iron scraphaving the desired carboncontent of sufficient ferro'silicon having a silicon content of from 10%to 20% to deoxidize the bath and also to protect from oxidation theadded chromium, then adding the desired amount of ferrochrome.

A process of the character described comprising the addition to a bathcomposed of pig iron and iron scrap having the desired carbon content ofsuflicient ferrosilicon having a silicon content of from 10% to 20% todeoxidize the bath and also to protect from oxidation the added chr0-mium, then adding the desired amount of ferrochrome, then after thechromium is melted adding other ferro alloys as desired, and thentapping the heat.

In testimony whereof, I have hereunto signed my name.

NAPOLEON PETINOT.

